Method and apparatus for determining a deterioration of respiratory function

ABSTRACT

In accordance with one embodiment of the invention, a system is provided for the monitoring of blood analytes using optical probes in the circulatory system. The probes can be inserted on the venous side of the circulatory system. In another embodiment, methods and apparatuses can be used for processing continuous information generated from indwelling intravascular or tissue optical sensors including, but not limited to, measuring gas concentrations, pH, temperature, and other analytes of blood or tissue. In another embodiment, analyte values can be displayed and analyzed to determine if the values fall outside of normal physiological parameters. Trends of one or multiple analyte values can be analyzed and extrapolated to predict any impending, deleterious condition. In one embodiment, an alarm can be transmitted to appropriate personnel when criterion/criteria are met. In yet another embodiment, devices can be inhibited from delivering continuous infusions of medicine to patients.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application61/021,094 filed on Jan. 15, 2008 entitled “Measurement of CarbonDioxide Using Optical Probes in Peripheral Venous System” the content ofwhich is hereby incorporated by reference in its entirety and for allpurposes.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH OR DEVELOPMENT

NOT APPLICABLE

REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISK

NOT APPLICABLE

BACKGROUND

In the last decade, there has been a significant increase of hypoxicbrain injuries and deaths in hospitalized patients who have receivedintravenous opioids, commonly referred to as narcotics, for pain controlafter surgery, a phenomenon entitled postoperative opioid-inducedrespiratory depression. Narcotics diminish the brain's sensitivity tocarbon dioxide (CO₂). The normal physiological response to rising levelsof CO₂ is hyperventilation, the body's method to exhale excess carbondioxide. Paradoxically, in the presence of narcotics, the brain signalsthe respiratory system to breath less frequently than during normalrespiration—a dangerous situation. As CO₂ in the blood rapidlyincreases, respiratory depression and apnea, the cessation of breathing,follow with resultant brain injury or death. Patients receivingintravenous narcotics in a hospital setting are at a higher risk ofrespiratory depression as opposed to those who have surgery in anoutpatient ambulatory surgicenter. Outpatients are at decreased risk forrespiratory depression because they typically have less invasivesurgeries and receive weaker, therefore less dangerous, oral narcoticsfor pain relief. Per standard protocol, hospitalized patients receivepowerful intravenous narcotics for pain suppression immediatelyfollowing surgery. At highest risk for postoperative opioid-inducedrespiratory depression are geriatric, debilitated and/or obese patientpopulations, all of who are susceptible even to routine administrationof intravenous narcotics. Similarly, patients who suffer from sleepapnea, 85% of who have not been diagnosed, or individuals habituated tonarcotics, are also likely to experience depression of breathing.Furthermore, the patient population is growing older, and as acorollary, increasingly debilitated—another risk factor for respiratorydepression. In the United States alone, the number of hospitalizedpatients at-risk for postoperative opioid-induced respiratory depressionis on the order of several million per year.

It is well established moment-to-moment, that both oxygen and carbondioxide, so called blood analytes, are critical values in the immediatehealth and well being of an individual. One non-invasive modality, pulseoximetry, a technology measuring the percent of hemoglobin saturatedwith oxygen, is routinely utilized in hospital and outpatient settingsto monitor oxygenation as an ongoing reflection of respiratory status.

Unfortunately, it has been repeatedly demonstrated that when a patientis experiencing diminution of his respiratory status, monitoring withcontinuous pulse oximetry often gives insufficient warning to medicalpersonnel to intervene in a timely fashion to prevent injury or death.As a result, there has been an epidemic of anoxic brain injuries anddeaths from respiratory depression and/or arrest of monitored patientsin hospitals. By the time the hospital staff is alerted, the patient, inmany instances, is already in a dangerous condition.

A conference of 100 physician and scientists convened in 2006 to studypostoperative opioid-induced respiratory depression found no medicaldevices currently available to adequately address the problem. Despitenational recognition of this issue, it has yet to be sufficientlysatisfied. Numerous technologies have attempted to monitor carbondioxide; a gas, which builds up precipitously in the blood stream—and,consequently, the brain—when breathing is compromised and themeasurement of this analyte is considered the gold standard forassessing ventilation. Most of the modalities employed for bedsidemonitoring of carbon dioxide are non-invasive and measure the end tidalcarbon dioxide at the nose or mouth. These have been proven to beinsufficient primarily because they don't assess the volume or qualityof breathing. For example, they only measure the number of exhalations,i.e. breathing rate, rather than the volume of carbon dioxide actuallybeing exhaled.

Another modality currently in clinical trials, an adhesive acousticsensor placed over the larynx, extracts respiratory physiologic datafrom ambient sound vibrations occurring at the skin's surface, tocalculate the respiratory rate. Again, the depth or quality of eachbreath cannot be evaluated. Numerous studies attempting to use apneamonitors, an alarm triggered by breathlessness, have been inadequate.One of the serious downfalls of these various trials has been the highnumber of false positive alarms. Studies incorporating simultaneous useof two or more of these modalities have not been entirely successfuleither.

As noted, one of the serious historical problems was the high number ofalarms, particularly false positives. Life safety personnel must respondto false alarms before being able to determine that the alarm isactually a false one. This takes life safety personnel away from theirother duties and creates less confidence among staff in the monitoringequipment. As a result, some manufacturers have provided selectabledelays (for pulse oximeters, for example) so as to reduce the number offalse alarms. However, this necessarily produces a further delay inresponding to true alarms. Namely, a pulse oximeter that has beenconfigured to delay the signaling of an alarm or even to inhibit thesignaling of an alarm so as to avoid a false positive alarm willnecessarily delay the signaling of a true alarm and thus increase thetime period before life safety personnel can respond to the patient'scondition.

Response time is critical in being able to maintain a patient in stablecondition. For example, human physiologic stability is maintained bycomplex and interactive physiologic systems. This includes theinteractive nature of the human respiratory system and cardiac system.When a respiratory arrest occurs, the body is deprived of additionaloxygen intake. Eventually, unless respiration is restored, the patientwill suffer a cardiac arrest. It is much more difficult to revive apatient that has suffered a dual arrest (i.e., both respiratory andcardiac arrest) than it is to revive a patient that has suffered onlyrespiratory arrest. Thus, it is quite clear that the ability to respondto a respiratory arrest as quickly as possible is of benefit to thepatient. Moreover, one can appreciate that given the highly interactivenature of physiological systems that in many instances a meredeterioration in respiration can result in damage to physiologicalsystems and tissue.

SUMMARY

In accordance with one embodiment of the invention, a system is providedfor the monitoring of blood analytes using optical probes in thecirculatory system. In accordance with one embodiment, the probes can beinserted on the venous side of the circulatory system.

In accordance with another embodiment, a method is provided formonitoring at least one blood analyte for use in determining adeterioration of respiratory function. The method comprises obtaining avenous blood analyte measurement of a patient and determining adeterioration of respiratory function based upon the venous bloodanalyte measurement.

In accordance with another embodiment, a method of monitoring at leastone blood analyte for use in determining a deterioration of respiratoryfunction comprises inserting an optical probe into a tissue bed of apatient; obtaining a blood analyte measurement from said tissue bed; anddetermining a deterioration of respiratory function based upon saidblood analyte measurement.

In accordance with another embodiment, an apparatus comprises a sensorfor sensing a venous blood analyte measurement of a patient and aprocessor programmed to determine a deterioration of respiratoryfunction based upon said venous blood analyte measurement.

In accordance with another embodiment, an apparatus comprises an opticalprobe for insertion into a tissue bed of a patient; wherein said opticalprobe is configured for sensing a blood analyte measurement from saidtissue bed; and a processor configured for determining a deteriorationof respiratory function of said patient based upon said blood analytemeasurement.

In accordance with another embodiment, methods and apparatuses can beused for processing continuous information generated from in-dwellingintravascular or tissue optical sensors including, but not limited to,measuring gas concentrations, pH, temperature, and other analytes ofblood or tissue.

In accordance with another embodiment, analyte values can be displayedand analyzed to determine if the values fall outside of normalphysiological parameters. Trends of one or multiple analyte values canbe analyzed and extrapolated to predict any impending, deleteriouscondition.

Further embodiments of the invention will be apparent from thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a patient being monitored withblood analyte optical probes, in accordance with one embodiment of theinvention.

FIG. 2 illustrates a block diagram of a computing device that can beutilized as the computer shown in FIG. 1, in accordance with oneembodiment of the invention.

FIG. 3 illustrates a flow chart demonstrating a method of determining adeterioration of respiratory function in accordance with one embodimentof the invention.

FIGS. 4A, 4B, and 4C illustrate a flow chart demonstrating a method ofdetermining a deterioration of respiratory function in accordance withone embodiment of the invention.

FIG. 5 illustrates a flow chart demonstrating a method of determining adeterioration of respiratory function by measuring a blood analyte froma tissue bed of a patient, in accordance with one embodiment of theinvention.

FIG. 6 illustrates a flow chart demonstrating a method of determining adeterioration of respiratory function by measuring a blood analyte froma tissue bed of a patient, in accordance with one embodiment of theinvention.

FIG. 7 illustrates an optical probe inserted via a catheter inaccordance with one embodiment of the invention.

FIG. 8 illustrates a computerized monitoring of an optical probeinserted into the circulatory system of a patient in accordance with oneembodiment of the invention.

DETAILED DESCRIPTION

As noted above, pulse oximetry is one method commonly used to monitor apatient's respiratory condition. However, pulse oximetry can be slow todetect a change in a patient's respiratory condition. It does notmeasure the critical ventilatory value CO₂ in the patient's blood. Sucha delayed detection can quickly result in a deleterious respiratorycondition for the patient. This is particularly true for patients in asurgical setting; but, it also applies to patients in a non-surgicalsetting.

In accordance with one embodiment of the invention, the monitoring of ablood analyte can be used to readily detect a change in a patient'srespiratory condition. Such blood analytes can include: (1) the partialpressure of oxygen in the patient's blood (oftentimes designated aspO₂), (2) the partial pressure of carbon dioxide in the patient's blood(oftentimes designated as pCO₂), (3) the acid/base value of thepatient's blood (oftentimes designated as pH), and/or (4) thetemperature of the patient's blood, (5) lactic acid of the patient'sblood, as well as other blood analytes.

The detection of the partial pressure of a gas in the patient's blood isquite different from pulse oximetry. Pulse oximetry is a non-invasivetechnique that measures the percent of hemoglobin saturated with oxygen(oftentimes referred to as the pulse oximeter oxygen saturation anddesignated as S_(p)O₂) in the patient's blood. In contrast, themeasurement of the partial pressures of both blood gases (such as pO₂and pCO₂) is a more accurate indicator of the patient's currentrespiratory status when compared to S_(p)O₂.

Similarly, current techniques for monitoring the amount of CO₂ in apatient's blood have significant drawbacks. Numerous technologies havebeen used in attempts to monitor carbon dioxide. Most of the modalitiesemployed for bedside monitoring of carbon dioxide are non-invasive andmeasure the end tidal carbon dioxide at the nose or mouth. These havebeen proven to be insufficient primarily because they don't assess thevolume or quality of breathing. For example, they only measure thenumber of exhalations, i.e. breathing rate, rather than the volume ofcarbon dioxide actually being exhaled. In contrast, measuring thepartial pressure of CO₂ (pCO₂) provides an accurate reflection of bloodCO₂ levels.

Optical Probes

In accordance with one embodiment of the invention, LED powered opticalprobes, or an equivalent light source, can be used to monitor bloodanalytes for the early detection of deleterious blood conditions. Forexemplary purposes, this embodiment of the invention will be describedwith reference to the buildup of carbon dioxide in the blood and thedamaging effect that carbon dioxide can have on the human body. However,it should be noted that in accordance with some embodiments of theinvention that other conditions could be detected.

Historically, in biomedicine, the use of invasive optical sensors (oroptode systems) for the detection and monitoring of physical andchemical parameters inside an animal or human date back to the 1960's.Many of these optical systems use one or multiple optical fibers for thecontinuous measurement of intravascular or tissue bed parameters, socalled analytes, including but not limited to pH, temperature, andpartial pressures of oxygen and carbon dioxide.

In the past, use of such optical sensors has not met with sustainedcommercial success. One explanation is that the optical systems requiredthe use of expensive optical components to select light of specificwavelengths from a broad spectrum source. The cost of such a lightsource did not permit optical sensors to be readily used in a healthcaresetting. Another aspect was the large size of the base unit, whichhoused the bulky light source, electronics, and microprocessor. As aresult, use of such optical sensors has subsided and to this day it hasbeen passed over for more user-friendly technologies.

One type of sensor that has been used in the past is the optical probe.Optical probes are miniature devices that can be inserted via a catheterinto an artery in order to measure blood analytes. As noted, suchoptical probes have required the use of expensive optical components toserve as the light source. This increased the cost of the optical probesystem and also made it bulkier and difficult to operate. In accordancewith one embodiment of the invention, the former light source can now bereplaced, e.g. with an LED. The LED serves as a convenient, effective,compact and inexpensive light source. Furthermore, it allows the opticalprobe to now be used in a vastly greater number of settings, includingthe use by paramedics in the field and in ambulances.

Venous Side Measurement

The preferred standard of objectively measuring ventilation hashistorically been the monitoring of carbon dioxide in the blood streamon the arterial side of the circulatory system. As breathing diminishes,the pressure of carbon dioxide (pCO₂) in the blood rises. The CO₂ isimmediately converted into carbonic acid, a portion of which isbuffered. As a consequence once the buffers are exhausted, the pH in theblood essentially falls in lock-step fashion with the rise in carbondioxide, although there are other lesser contributors to acidemia, e.g.,lactic acid from anaerobic tissue metabolism. Thus, in the setting of anacute respiratory event, measurement of pH in the blood is an indirectreflection of ventilation.

Measurement on the arterial side of the circulatory system has beenpreferred in the past because the pressure of oxygen in the blood,(pO2), was preferentially assessed before delivery and extraction by thetissues as occurs on the venous side, and is therefore an easilyinterpreted measure of lung function. For a multitude of reasons, venouspO2 is subject to much greater variation and therefore not as valuableas a single measurement.

As a result of this preference for taking measurements on the arterialside of the circulatory system, the overwhelming majority of opticalsensors in human and animal studies were inserted in arteries in orderto collect data for those studies. Besides being painful, insertion of aprobe into an artery requires a highly skilled operator, generally aphysician, to perform the task. Also, a puncture in artery, thehigh-pressure side of the vascular system, often resulted in significanthematoma formation or significant hemorrhage in the case of unrecognizeddislodgement.

A minority of the intravascular optode system studies examined data fromthe central venous circulation. Access to the central venous circulatorysystem requires the skills of a physician specifically trained in thispractice and moreover, is dangerous, even potentially fatal.

Rare studies have examined information generated from an indwellingoptode system in the peripheral venous circulatory system. Such useshave been research purely oriented, rather than for treatment. Thus,none has been for the sole purpose of recognizing the critical buildupof carbon dioxide and triggering the necessary remedial action.

In accordance with another embodiment of the invention, the use of thevenous system is actually encouraged rather than avoided. In fact, inaccordance with one embodiment, one can utilize venous monitoringwithout utilizing arterial side monitoring.

Probe Insertion and Positioning

Peripheral veins are generally quite accessible and placement of anintravenous catheter is relatively easy. By mandate, virtually allpatients residing in a hospital will have an indwelling intravenouscatheter, usually peripheral in position, at all times. The size of anoptical probe, generally less than 100 microns, allows easy insertioninto the peripheral venous system through a small catheter to monitorblood analytes in accordance with this embodiment of the invention.Optical sensor studies of peripheral venous blood have yielded a strongconcordance of pCO2 and pH values with simultaneously drawn centralvenous and arterial blood analyzed by conventional means. Thus, theinsertion can place the probe in the peripheral system where bloodanalytes are measured.

Furthermore, it is noted that since patients often will have aperipheral venous system IV, that the insertion of an optical probe viasuch an IV may not necessitate a further invasive procedure on thepatient. Rather, the existing IV, via a sideport device, can be used forinsertion of the optical probe. In addition, the peripheral IV can beused to insert optical probes into the central venous system by routingan optical probe through the peripheral system to where it joins thecentral venous system. Thus, one can advance the optical probe all theway to the central venous position without having to perform an invasiveand potentially dangerous procedure directly into the central venoussystem. Nevertheless, in some instances, one might choose to use acentral venous catheter for inserting a probe.

Thus, a variety of options are available for positioning a probe.Namely, one could utilize peripheral venous insertion and takemeasurements from a peripheral venous location. Or, one could utilize aperipheral venous insertion and take measurements from a central venousposition. Or, one could utilize a central venous insertion and takemeasurements from a central venous position.

In accordance with another embodiment, one could take measurements froma tissue bed. Thus, one could insert a probe subcutaneously into anorgan (such as the brain), a muscle (such as the patient's deltoidmuscle), or interstitial fluid (i.e., fluid that bathes a cell). Suchtissue beds can provide blood analyte values that can reflect therespiratory status of the patient. Thus, they may provide a more usefulposition for obtaining blood analyte values under given conditions.

Monitoring

While others have attempted to rely purely on pulse oximetry to monitorrespiratory status, there is clearly a need for an earlier detectionsystem. Thus, in accordance with another embodiment of the invention,multiple continuous blood analyte values can be measured, compared, andinterpreted. This will allow a system to have a higher degree ofsensitivity. Furthermore, more exacting criteria may be used for alarmconditions. Thus, the number of false positive alarms can bedecreased—resulting in a greater confidence in the alarm condition byhealthcare personnel.

The ability to analyze continuous measurement of appropriate bloodanalyte values, particularly carbon dioxide and pH can be invaluable inthe determination of a patient's respiratory status. It facilitatesearly detection of respiratory and/or cardiac deterioration, allows forearlier signaling of an alarm to appropriate medical personnel forlife-saving intervention, and allows immediate inhibition of anymedicine infusions or devices connected to the patient deemed to bedeleterious. In addition to inhibition of a medicine, it can alsoprovide for the administration of a substance to increase respiration.

This embodiment can utilize continuous data generated from anintravascular optical fiber or optode system, not only from arterial andcentral venous locations, but also preferably from the more easilyaccessible peripheral venous system. This information serves as input toa computer, such as a microprocessor-based device. Another embodimentmay utilize additional sources of continuous medical information fromother devices for integration and analysis, such as, but not limited to,an electrocardiogram, pulse oximetry and temperature.

The measurement of lactic acid is one example of how continuous data canbe processed to determine the deterioration of a patient's homeostasis.Namely, a probe to measure lactic acid may be inserted into thepatient's circulatory system. The probe may continuously take lacticacid measurements for use in determining if the build-up of lactic acidis occurring. In accordance with pre-determined criteria that indicatethat an increase in anerobic metabolism is occurring, a computer couldsignal an alarm to life safety personnel and also take proactivemeasures to reevaluate the patient's status.

Numerous studies confirm that measurements of pH and carbon dioxide froma peripheral vein closely approximate simultaneous values taken fromarterial and central venous circulations; therefore continuouslymeasuring peripheral venous blood analytes can reflect the currentrespiratory status and health of the patient. This has apparently notbeen appreciated in the prior art nor has statistical analysis of thesereal-time and historical values and trends been used to detectdeleterious trends, particularly those of impending respiratory failureand, but not limited to, heart failure, sepsis, ARDS, etc. and/or otherorgan systems as well.

In accordance with another embodiment of the invention, when thisinformation, real or derived, falls outside of established safe ranges,and/or extrapolation of trends suggest or verify deleterious trends, analarm condition can be triggered. The alarm can be immediatelytransmitted via electronic means, preferably wirelessly, to a receiver,for example a paging system, alerting appropriate medical personnel andallowing early life-saving intervention.

In accordance with another embodiment, false positive and false negativealarms can be reduced. By analyzing a greater amount of data, whether itbe a continuous amount of data, multiple sources of data, multipletrends, or multiple variables, a more accurate determination of adeleterious condition can be determined. Thus, this results in fewerfalse positive and false negative alarms being generated reducing therisk of medical personnel becoming weary or even worse, jaded fromincessant alarm conditions.

In accordance with still another embodiment of the invention, devicesdelivering infusions of medicine, such as narcotics, can be turned offimmediately upon detection of an alarm. Similarly, other devicesconnected to the patient could also be turned off immediately upondetection of an alarm. In the situation where a narcotic was beingadministered, for example, a detection of an excessive amount of carbondioxide in the blood could trigger the immediate and automatic cessationof the narcotic. This would allow hospital personnel to respond to thealarm to determine if the alarm was accurate and also allow remedialaction to be taken while the hospital personnel are in transit to thepatient's room. Remedial action could include the automaticadministration of a substance to increase respiration.

Thus, the monitoring system can be used to predict a variety ofconditions. It may be used to determine a deterioration of a respiratoryfunction. It may be used to predict a proximate respiratory event, suchas a respiratory arrest. It may also be used to predict opioid inducedrespiratory depression. It may be used to turn off the administration ofsuch opioids. And, it may be used to control the administration ofsubstances that increase respiration. Finally, it can be used to signallife safety personnel.

The monitoring can take place in a variety of settings. For example, itcan take place in a surgical setting, a non-surgical setting, orambulatory care setting. It can also be used in a setting where opioidsare administered. For example, it can be used by dentists who administeropioids during dental procedures.

Referring now to FIG. 1, a system 100 in accordance with one embodimentof the invention can be seen. FIG. 1 shows a patient coupled with anoptical probe “A”. The optical probe is inserted via an IV catheter intothe patient's peripheral venous system. The probe utilizes an LED, orequivalent light source, for measuring at least one or more bloodanalytes simultaneously, such as pH, pO2, pCO2, or temperature. A signalcan be transmitted from the probe to a computer, such as computer 104.Computer 104 can then utilize the signal in a variety of ways.

For example, computer 104 can perform trend analysis of the signal todetermine the accumulation of carbon dioxide in the respiratory system.Similarly, computer 104 can utilize additional measurements. Forexample, measurements can be taken from other locations on the patient'sbody, such as the umbilical artery, central venous system, peripheralarterial system, or tissue beds such as the brain, as shown by theprobes labeled “D”, “B”, “C” and “E,” respectively. Those measurementscan be compared against one another as desired.

Similarly, measurement of different blood analytes and biologicalindicators can be used in conjunction with one another. For example,pulse oximetry measurements can be used in conjunction with measurementof carbon dioxide levels and EKG values. Thus, in some situations, onecan check two or more different analyte values in conjunction with otherbiologic measurements for indications of the accumulation of carbondioxide prior to signaling an alarm or implementing remedial measures.In one embodiment, those two or more analyte values can be comparedagainst pre-determined ranges for each analyte value. Similarly, one canuse the EKG device 120 or other patient monitoring devices, such as apulse oximeter, to further detect dangerous conditions. FIG. 1 showsthat computer 104 can be coupled with a memory device, such as adatabase 108. The database can store trended data for analysis. Amedicine dispenser 112 is shown coupled with the computer. The medicinedispenser can dispense narcotics, for example. When an alarm situationis detected, the medicine dispenser can be controlled so as to inhibitthe administration of the medicine. An alarm 116 is also shown coupledwith the computer. The alarm can be any alarm that signals medicalpersonnel to respond to the patient' condition. For example, it can be awireless alarm device, e.g. a pager, carried by hospital personnel.

The computer used in system 100 can be a microprocessor based device.Furthermore, the computer can be sized so as to allow for portabilityand use in locations remote from a hospital, such as by paramedics orflight-for-life personnel.

FIG. 2 illustrates an embodiment of a computer device that could beutilized to implement the computerized device shown in FIG. 1, inaccordance with one embodiment of the invention. System 200 is showncomprised of hardware elements that are electrically coupled via bus208, including a processor 201, input device 202, output device 203,storage device 204, computer-readable storage media reader 205 a,communications system 206 processing acceleration (e.g., DSP orspecial-purpose processors) 207 and memory 209. Computer-readablestorage media reader 205 a is further coupled to computer-readablestorage media 205 b, the combination comprehensively representingremote, local, fixed and/or removable storage devices plus storagemedia, memory, etc. for temporarily and/or more permanently containingcomputer-readable information, which can include storage device 204,memory 209 and/or any other such accessible system 200 resource. System200 also comprises software elements (shown as being currently locatedwithin working memory 291) including an operating system 292 and othercode 293, such as programs, applets, data and the like.

System 200 has extensive flexibility and configurability. Thus, forexample, a single architecture might be utilized to implement one ormore servers that can be further configured in accordance with currentlydesirable protocols, protocol variations, extensions, etc. However, itwill be apparent to those skilled in the art that embodiments may wellbe utilized in accordance with more specific application requirements.For example, one or more system elements might be implemented assub-elements within a system 200 component (e.g. within communicationssystem 206). Customized hardware might also be utilized and/orparticular elements might be implemented in hardware, software(including so-called “portable software,” such as applets) or both.Further, while connection to other computing devices such as networkinput/output devices (not shown) may be employed, it is to be understoodthat wired, wireless, modem and/or other connection or connections toother computing devices might also be utilized.

One embodiment of the invention can utilize optical probes such as thosedescribed in U.S. Pat. Nos. 5,335,305; 5,397,411; and/or 5,408,999.FIGS. 7 and 8 illustrate how such probes might be used in accordancewith one embodiment of the invention. Namely, FIGS. 7 and 8 show a probe700 that has been disposed in an intra-venous cannula 701. The cannula701 is suitable for introduction into and disposition within a humanblood vessel. A tip of the probe maybe disposed in the cannula (e.g.when the cannula resides in a vein) by connecting the luer y connector702 to the cannula and then inserting the probe 100 into the cannulathrough one channel 707 of the luer y connector. Whatever fluid is beingintroduced into or withdrawn from the cannula may be introduced orwithdrawn from channel 705 of the luer y connector through which theprobe 700 does not extend.

As shown in FIGS. 7 and 8, the probe 700 may then be connected to asensor interface unit 820 (shown as separate from a base unit but whichcould be incorporated therein) which is connected to a base unit 104(also shown as computer 104 in FIG. 1). The sensor interface unitprovides light input to the probe and detects and measures light comingout of the probe. Signals from the unit 820 are then fed into the baseunit where they are processed for display, recordation, ormonitoring—especially for determining the deterioration of respiratoryfunction.

Probe 700 may have a bundle of optical fibers 832 which extend throughconnector 730. The probe's bundle of fibers may be glued into a maleluer with adhesive. The connector 730 is made preferably from polycarbonate plastic. The tube 840 is made preferably from polyethylene andextends from the connector 730 to a junction box 831.

Referring now to FIGS. 3-6, various embodiments are illustrated. FIG. 3shows a high level flow chart 300 that illustrates a method ofdetermining a deterioration in respiratory function. In block 304, ablood analyte measurement is taken from the patient. As explained above,the measurement is preferably taken from the venous system of thepatient. In block 308, the blood analyte measurement can be used todetermine if a deterioration of respiratory function is occurring or hasalready occurred.

A more detailed flow chart 400 can be seen in FIGS. 4A, 4B, and 4C whichillustrates a more detailed embodiment for taking and analyzing bloodanalyte measurements. A venous blood measurement can be taken in avariety of care settings. By way of example only, the measurements canbe taken in a non-surgical setting, a surgical setting, or an ambulatorycare setting. The method could be practiced in other settings as well.

To obtain a measurement, an optical probe is one type of transducer thatcan be used. Such an optical probe can be coupled to the patient in avariety of ways. For example, an optical probe can be inserted via acatheter in a peripheral vein of a patient, as shown by block 420. Sucha catheter is often present on individuals admitted to a hospital. Thus,it provides an easily accessible access point. The probe can bepositioned within the patient's circulatory system in a variety oflocations. For example, block 424 shows that the probe can be positionedwithin the patient's peripheral venous system, such as within a vein inthe patient's forearm. The probe might also be advanced through thepatient's peripheral venous system to the patient's central venoussystem, as shown by block 428. This would allow a peripherally insertedprobe to obtain a measurement from the central venous system, such asfrom the patient's subclavian vein, as shown by block 432.Alternatively, or additionally, a probe could be inserted into a centralvein of a patient, as shown by block 436. In such an instance, ameasurement could be obtained from the central venous system, as shownby block 440.

Once the transducer (such as an optical probe) is coupled to thepatient, a measurement of a blood analyte can be taken. Block 444 showsthat the partial pressure of carbon dioxide in the blood of the patientcan be measured. Similarly, block 448 shows that the partial pressure ofoxygen in the patient's blood can be measured. And, blocks 452 and 456illustrate that the pH and temperature of the blood of the patient canbe measured, respectively. In accordance with one embodiment, thesemeasurements are preferably taken on the venous side of the patient'scirculatory system.

The patient's condition may be monitored so as to evaluate his/hercondition. In block 460, a determination of a deterioration ofrespiratory function can be made based upon the blood analytemeasurement. Block 468 shows that trend analysis(ses) can be used basedupon the blood analyte measurements. For example, the measurement(s) canbe used to predict if the patient is approaching a respiratory arrest,as shown by block 468. Or, the measurement(s) can be used to determineif the patient is approaching respiratory depression, such as opioidinduced respiratory depression, as shown by block 472.

It should be noted that block 476 highlights that this method can beperformed on patients that are not under mechanical ventilationassistance. Thus, the early detection of a deterioration of respiratoryfunction can be important for patients in such a situation as there isno on-going ventilation assistance coupled to the patient that couldassist the patient prior to detecting the patient's condition.

In response to the determination that the patient's respiratory functionhas deteriorated, a variety of measures could be implemented. Forexample, block 480 illustrates that the administration of at least oneopioid to the patient could be reduced and block 488 illustrates theadministration of at least one opioid to the patient could be ceased.Alternatively, proactive measures could be taken to increase therespiration of the patient, as shown by block 492. This could includethe administration of a medicine to cause the patient's system torespire more frequently. Or, it could involve the administration of moreoxygen to the patient. Block 496 also illustrates that life safetypersonnel could be contacted via signaling an alarm—such as transmittingan electrical signal to an alarm system.

In accordance with one embodiment of the invention, blood analytemeasurement can be determined in ways other than inserting a transducerinto a vein or artery of a patient. For example, flow chart 500 in FIG.5 shows that a measurement can be obtained by utilizing a tissue bed ofthe patient. The tissue bed can be an organ, a muscle, or interstitialfluid of the patient. A transducer, such as an optical probe, can beinserted into the tissue bed as shown by block 504. Once in place, theprobe can obtain a blood analyte measurement from the tissue bed, asshown by block 512. From the blood analyte measurement, a determinationcan be made as to whether there is a deterioration in respiratoryfunction of the patient.

FIG. 6 illustrates a more detailed flow chart 600 in accordance with oneembodiment. In block 604, a transducer, such as an optical probe, isinserted into a tissue bed of a patient. The optical probe can beinserted for example into an organ, interstitial fluid, brain tissue,subcutaneous tissue, or muscle, as illustrated by blocks 608, 612, 616,620, and 624 respectively. One possible choice for muscle insertion is adeltoid muscle of the patient, as shown by block 628.

Once the probe is inserted into the tissue bed, a blood analytemeasurement can be taken, as shown by block 632. Then, a determinationcan be made as to whether there is or has been a deterioration ofrespiratory function of the patient based upon the blood analytemeasurement.

While the illustrative embodiment used above has referred to a humanpatient, it should be noted that the systems and methods describedherein could also be applied to non-human patients, as well. Thus, theuse for veterinary medicine is also applicable. Also this system may beused to monitor experimentally created milieus in a research format,whether living or non-living.

While various embodiments of the invention have been described asmethods or apparatus for implementing the invention, it should beunderstood that the invention can be implemented through code coupled toa computer, e.g., code resident on a computer or accessible by thecomputer. For example, software and databases could be utilized toimplement many of the methods discussed above. Thus, in addition toembodiments where the invention is accomplished by hardware, it is alsonoted that these embodiments can be accomplished through the use of anarticle of manufacture comprised of a computer usable medium having acomputer readable program code embodied therein, which causes theenablement of the functions disclosed in this description. Therefore, itis desired that embodiments of the invention also be consideredprotected by this patent in their program code means as well.Furthermore, the embodiments of the invention may be embodied as codestored in a computer-readable memory of virtually any kind including,without limitation, RAM, ROM, magnetic media, optical media, ormagneto-optical media. Even more generally, the embodiments of theinvention could be implemented in software, or in hardware, or anycombination thereof including, but not limited to, software running on ageneral purpose processor, microcode, PLAs, or ASICs.

It is also envisioned that embodiments of the invention could beaccomplished as computer signals embodied in a carrier wave, as well assignals (e.g., electrical and optical) propagated through a transmissionmedium. Thus, the various information discussed above could be formattedin a structure, such as a data structure, and transmitted as anelectrical signal through a transmission medium or stored on a computerreadable medium.

It is also noted that many of the structures, materials, and actsrecited herein can be recited as means for performing a function or stepfor performing a function. Therefore, it should be understood that suchlanguage is entitled to cover all such structures, materials, or actsdisclosed within this specification and their equivalents, including thematter incorporated by reference.

It is thought that the apparatuses and methods of embodiments of thepresent invention and its attendant advantages will be understood fromthis specification. While the above description is a completedescription of specific embodiments of the invention, the abovedescription should not be taken as limiting the scope of the inventionas defined by the claims.

1-20. (canceled)
 21. A method of monitoring at least one blood analytefor use in determining a deterioration of respiratory function, saidmethod comprising: inserting an optical probe into a tissue bed of apatient; obtaining a blood analyte measurement from said tissue bed;determining a deterioration of respiratory function based upon saidblood analyte measurement.
 22. The method as claimed in claim 21 whereinsaid inserting said optical probe into said tissue bed of said patientcomprises inserting said optical probe into an organ.
 23. (canceled) 24.The method as claimed in claim 21 wherein said inserting said opticalprobe comprises inserting said optical probe into brain tissue of saidpatient.
 25. The method as claimed in claim 21 wherein said insertingsaid optical probe comprises inserting said optical probe intosubcutaneous tissue of said patient.
 26. The method as claimed in claim21 wherein said inserting said optical probe comprises inserting saidoptical probe into a muscle of said patient.
 27. The method as claimedin claim 26 wherein said inserting said optical probe comprisesinserting said optical probe into a deltoid muscle of said patient.28-51. (canceled)
 52. A method comprising: inserting an optical fiberprobe into interstitial fluid of a patient; taking a series ofinterstitial fluid CO₂ measurements with the optical fiber probe;performing a trend analysis with a processor by utilizing the series ofinterstitial fluid CO₂ measurements; determining a value of the currentamount of CO₂ in the respiratory system of the patient from the trendanalysis; signaling an alarm system if the value of the current amountof CO₂ in the respiratory system of the patient is in a predeterminedunsafe range for CO₂.
 53. A method comprising: inserting an opticalfiber probe into interstitial fluid of a patient; taking an interstitialfluid analyte measurement with the optical fiber probe; utilizing aprocessor to determine an interstitial fluid analyte value from theinterstitial fluid analyte measurement; wherein the processor isresponsive to a rule to compare the interstitial fluid analytemeasurement value with a predetermined unsafe range for the interstitialfluid analyte; and wherein the processor is responsive to a rule tosignal an alarm system based upon the comparison of the interstitialfluid analyte measurement value with the predetermined unsafe range. 54.The method as claimed in claim 53 wherein the interstitial fluid analyteis CO₂.
 55. The method as claimed in claim 53 wherein the interstitialfluid analyte is pH.
 56. The method as claimed in claim 53 wherein theinterstitial fluid analyte is O₂.
 57. The method as claimed in claim 53wherein the interstitial fluid analyte is pCO₂.
 58. The method asclaimed in claim 53 wherein the interstitial fluid analyte is pO₂. 59.The method as claimed in claim 53 wherein the utilizing the processor todetermine the interstitial fluid analyte value from the interstitialfluid analyte measurement comprises: performing a trend analysis withthe processor by utilizing a series of interstitial fluid CO₂measurements.
 60. A method of decreasing the risk of postoperativeopioid-induced respiratory depression comprising: inserting a firstoptical fiber probe into a peripheral venous system IV of apostoperative patient being treated with opioid(s); utilizing an LEDlight source with the first optical fiber probe; taking a series of CO₂blood analyte measurements with the first optical fiber probe;performing a trend analysis with a processor by utilizing the series ofCO₂ blood analyte measurements; determining a value of the currentamount of CO₂ in the respiratory system of the patient from the trendanalysis; inserting a second optical fiber probe into interstitial fluidof the patient; taking an interstitial fluid analyte measurement withthe second optical fiber probe; utilizing the processor to determinefrom the interstitial fluid analyte measurement a pH value for the bloodof the patient; utilizing the processor to determine from the currentamount of CO₂ in the respiratory system of the patient and pH value forthe blood of the patient that an increase in anerobic metabolism isoccurring indicating impending respiratory failure; in response to thedetermination that the increase in anerobic metabolism is occurring,signaling an alarm to life safety personnel; in response to thedetermination that the increase in anerobic metabolism is occurring,inhibiting the administration of the opioid(s) to the patient; inresponse to the determination that the increase in anerobic metabolismis occurring, administering medicine to cause the patient to respiremore frequently.
 61. A method comprising: inserting an optical fiberprobe into the venous system of a patient; taking a venous blood analytemeasurement with the optical fiber probe; utilizing a processor todetermine a venous blood analyte value from the venous blood analytemeasurement; wherein the processor is responsive to a rule to comparethe venous blood analyte value with a predetermined unsafe range for thevenous blood analyte; and wherein the processor is responsive to a ruleto signal an alarm system based upon the comparison of the venous bloodanalyte value with the predetermined unsafe range.
 62. The method asclaimed in claim 61 wherein the venous blood analyte is carbon dioxidein the venous blood of the patient.
 63. The method as claimed in claim61 wherein the venous blood analyte is partial pressure of oxygen in thevenous blood of the patient.
 64. The method as claimed in claim 61wherein the venous blood analyte is pH of the venous blood of thepatient.
 65. The method as claimed in claim 61 wherein the venous bloodanalyte is temperature of the venous blood of the patient.